Epstein-Barr Virus/(EBV) is emerging as one of the most important co-factors in AIDS/ARC. Reactivation of EBV is common in AIDS and AIDS patients frequently develop EBV- associated lymphomas. In addition, it has recently been shown that HIV can replicate in B-cells transformed by EBV, but not in EBV-negative B-cells. In this proposal the molecular interactions between EBV and HIV will be studied. Using the EBV-negative Burkitt Lymphoma lines Ramos and BJAB and several EBV converted counterparts of these cell lines, the replication of HIV and the expression of transfected HIV genes will be analysed. Cell lines expressing individual latent EBV proteins (EBNA1, EBNA2, EBNA3, LMP) will be created and analysed for their ability to support HIV replication. Binding and fusion experiments will be performed to determine if the receptor used for the uptake of HIV into B-cells is T4 or some other entity. The effect of HIV-infection on EBV-expression in latently infected cells will also be analyzed. In addition lymphoma cells from AIDS-patients will be characterized to determine how many of these lymphomas that are EBV-positive. The EBV-positive lymphomas will be analyzed for association with specific substrains of EBV and for restricted expression of the latent EBV- genes.